I goofed - if your 9 patch block is 9" finished, then your d9p block will be 8.5" finished (you only lose .5" with the center seam), and 8x9 blocks would measure 68 x 76.5 before borders.
I also cut my binding at 2.5" for a .5" binding. I've heard that judges like it thinner than that, but I think .5" looks good on a bed quilt.